Add Animation Blending / Transitions

[mrjshzk]

Targeted towards characters animations

Add a way to transition animations with blending times

• Should be optional of course
• Should be able to configure the blending time
• Should work per-instance

[antzGames]

The problem is not enough instanced uniforms to enable blending per instance in the shader. I am already using the instanced CUSTOM_DATA uniform.

Blending also will slow down the shader performance because you need to sample the VAT texture (at least 2x). The changes to the shader will also be moderately complex.

If you really need blending VAT support, you should check out: https://github.com/shadecoredev/AnimatedMultimeshInstance3D

This project supports blending BUT it only is supported on the FORWARD+ renderer. The way he gets it to work is that he splits each 32bit value of the RGBA in CUSTOM_DATA into 2x16bit values, so in essence he has 8 instanced uniforms to work with. Another draw back is that he does not support per instance ALPHA, like my implementation.

For me I want a solution that works for ALL Godot renderes. Blending is cool, but my first priority is to implement the framerate and isLooping in the animation tracks so it behaves like the Unity OpenVAT implementation.

Lets keep this issue open for discussion purposes.

[mrjshzk]

Yeah I figured this would be a tricky thing since INSTANCE_CUSTOM is only a vec4 and we can only store so much in it.
I think the only way to do this would be if Godot added more ways to have per instance uniforms. Or if OpenVAT itself had an option that "baked" all the animations and their transitions in the same file (or another texture for that matter)

[antzGames]

We also have INSTANCE_COLOR, which is another vec4, but it is still not enough for everything (need at least 3 more instanced floats).

Note: There is a proposal to add another INSTANCE_CUSTOM_2: godotengine/godot-proposals#8666

I have laid out a product roadmap.

Product Roadmap

Version	Status	Features
V0.0.1	✅Released	OpenVAT JSON file import. New OpenVATMultimeshInstance3D node. Basic instanced animation track control. Instanced alpha channel control. Roughness, Metallic, Normal Map texture support in shader.
V0.0.2	✅Released	Instanced isLooping and timestamp support using the INSTANCE_COLOR.rg fields.
V0.0.3	💀Cancelled	Animation blending support needs at a minimum 3 more instanced uniforms which Godot does not provide. Need to wait for godotengine/godot-proposals#8666